Rumours or fact?


flossie

Link Posted 23/08/2010 - 11:18
I've still had no satisfactory explanation as to how to make my 12-24 focus - even on infinity (which isn't that far away on that) in anything other than bright sunshine.

Improved AF is waaaay up on my priority list for a new camera - and I don't shoot birds/airplanes/etc that people usually have problems with, yet spend more time fighting AF than anything else.
Still shooting in the dark (literally and metaphorically)...

johnriley

Link Posted 23/08/2010 - 11:24
flossie wrote:
I've still had no satisfactory explanation as to how to make my 12-24 focus - even on infinity (which isn't that far away on that) in anything other than bright sunshine.

Improved AF is waaaay up on my priority list for a new camera - and I don't shoot birds/airplanes/etc that people usually have problems with, yet spend more time fighting AF than anything else.

Then something is clearly wrong. I was using the 12-24mm in all lighting conditions from darkest cellars to bright sunshine last week at Beamish, and there were no problems at all.

Back to be checked and repaired I think. If other lenses are OK, then your 12-24mm has the problem.
Best regards, John

johnriley

Link Posted 23/08/2010 - 11:26
An afterthought - you are using centre-point only focus? If not, then I suggest you do. Focus on your main subject, half press on shutter release to lock, recompose, fire shutter. Works every time.
Best regards, John

ChrisA

Link Posted 23/08/2010 - 11:59
Anvh wrote:
ChrisA wrote:
Well, it wasn't clear that you were talking about videoing a wedding.

Don't know where you read that?

It was in Don's response to my earlier comment about workarounds:
Don wrote:
ChrisA wrote:
Quote:
I prefer manual focus anyways.
Nothing worse than having af "Hunting" in low light when shooting a wedding... which happens, even when the camera is on a tripod.... and the subject really isn't moving much...

Agreed.

But Don, this is the year 2010.

Manual focus in those circumstances is now what we call a "work around".

It's comments like that, that make Pentax say to themselves... "ah well, guys, we don't need to bother for another few months, with customers like that".

I disagree.
Nobody yet has video cam on the market that will focus properly in all shooting situations.

I took from that that he was talking about shooting video.

Anvh wrote:
There simply isn't a camera that works flawlessly in all situation or is there?

Well of course there isn't. I know that very well

All I'm suggesting is that better would be better, and to blindly accept the necessity to use MF as perfectly Ok, is to communicate to the manufacturer that improvements in that area are unimportant.

I had a play with a Nikon D100 a couple of years ago, with a very ordinary consumer zoom on the front. It was much, much better at getting a quick, positive focus lock in a fairly dark room, than my K10D was, also just with a kit lens on it.

This isn't the rigorous scientific comparison that I'd normally insist on, admittedly, but I was left with the feeling that the Pentax AF struggled a lot more than the Nikon - and a fairly old Nikon at that.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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ChrisA

Link Posted 23/08/2010 - 12:01
johnriley wrote:
The AF we have already is brilliant - certainly in terms of focusing accurately in low light. It can focus in light as good as I can see in to hope to do it myself. Deep in the gloom of old buildings there's never a problem, except with the usual subjects that are just nor suitable for AF. Such as smooth featureless walls or certain types of pattern.

But you don't shoot moving objects much in low light, do you John?

I find the AF fine too for stationary things in low light.

Admittedly, shooting moving dancers in dark clubs as I sometimes do, is a much tougher ask, and of course, I've become reasonably good at the other techniques, but having to use them makes life a lot harder than I'd like.

'Brilliant' is definitely not a word I'd use about Pentax AF in the harder situations. 'Occasionally Ok', 'Generally frustrating' a lot more so.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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ChrisA

Link Posted 23/08/2010 - 12:05
johnriley wrote:
An afterthought - you are using centre-point only focus? If not, then I suggest you do. Focus on your main subject, half press on shutter release to lock, recompose, fire shutter. Works every time.

John, c'mon, I'm not that much of a newbie ...

As a matter of fact, I do use the centre point in all circumstances (often with the half-press and reframe technique), except for aircraft in flight.

The Auto AF point selection is then much more effective, since it will continue to find the aircraft even if you fail to track it exactly on the centre point.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Last Edited by ChrisA on 23/08/2010 - 12:19

johnriley

Link Posted 23/08/2010 - 12:25
Quote:
John, c'mon, I'm not that much of a newbie ...

No insult intended, but when looking for solutions I never assume any more than I already know. We can all learn things, including myself, and we can all have blank spots sometimes.

Using AF for aircraft in that way makes me wonder about the shutter delay though. Ideally we would release the shutter just before the ideal moment, to allow for maybe 100ms delay before the shutter actually fires.

With AF, the focus has locked and maybe 100ms later (plus our own reaction time) when the shutter releases, the plane is no longer in the same position.

I will try this as soon as the opportunity arises and see how it compares with the MF I would normally use for such situations. Until then, from my persepctive I am only musing on the possibilities.
Best regards, John

flossie

Link Posted 23/08/2010 - 12:40
johnriley wrote:

Then something is clearly wrong. I was using the 12-24mm in all lighting conditions from darkest cellars to bright sunshine last week at Beamish, and there were no problems at all.

Back to be checked and repaired I think. If other lenses are OK, then your 12-24mm has the problem.

I can't see how a particular lens can affect the AF abilites of a camera - I come back to my theory that Pentax never expect people to put one on a Kx...

anyway, I posted this random shot a while back to illustrate - should be easy-peasy, its Infinity. Not even particularly dark (just overcast). But instead, hunt-hunt-hunt-won't-lock-oh-I-give-up-MANUALSWITCH!




(yes, I know, I forgot the CPL that day...)

Oh well, I'm just going out now, will be back shortly with another lens that they probably didn't expect see on a Kx... really must buy a licence for Lightroom though!
Still shooting in the dark (literally and metaphorically)...
Last Edited by flossie on 23/08/2010 - 12:41

ChrisA

Link Posted 23/08/2010 - 12:49
johnriley wrote:
Quote:
John, c'mon, I'm not that much of a newbie ...

No insult intended,

I know, John, hence my ''

None taken, it just made me laugh.

Quote:
but when looking for solutions I never assume any more than I already know. We can all learn things, including myself, and we can all have blank spots sometimes.

Absolutely. Blank spots - I can truly claim some expertise there


Quote:
With AF, the focus has locked and maybe 100ms later (plus our own reaction time) when the shutter releases, the plane is no longer in the same position.

Indeed. My experience is that sharp results are considerably easier when they're flying past, rather than towards or away.

For example, this is dreadful, whereas this isn't.

I got lucky with this, which is better, but there were a lot more duds.
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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
.

ChrisA

Link Posted 23/08/2010 - 12:51
flossie wrote:
I can't see how a particular lens can affect the AF abilites of a camera - I come back to my theory that Pentax never expect people to put one on a Kx...

anyway, I posted this random shot a while back to illustrate - should be easy-peasy, its Infinity. Not even particularly dark (just overcast). But instead, hunt-hunt-hunt-won't-lock-oh-I-give-up-MANUALSWITCH!

Feel free to stop by sometime soon and see if it's the same on my K10D.
.
Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Elva

Link Posted 23/08/2010 - 13:14
I see that many seem to have some problems in low light auto and manual focus. Use this; always focus with the longest range of your zoom lens then zoom out to the zoom setting that you want to use. Ie. 18 -85 lend focus at 85 zoom out to 18.....same for any lens. Works well.
I can shoot it ....

rparmar

Link Posted 23/08/2010 - 13:49
ChrisA wrote:
'Brilliant' is definitely not a word I'd use about Pentax AF in the harder situations. 'Occasionally Ok', 'Generally frustrating' a lot more so.

Yes, but the thing is, people shooting every other brand say the same. I am all for improved AF (who wouldn't be?) but the truth is I prefer MF and the control it gives. There is no way I expect a camera to know more than I do or to be faster than I am. Maybe someday it will get to that point, but it's more fun this way, so I'm not losing sleep over it.

(I have done paid gigs of children dancing, with six or more kids on stage at a time and only two or three minutes to get a great shot of each one. Quick movements in poor light. So I do know what it is like!)
Listen to my albums free on BandCamp. Or visit my main website for links to photography, etc.

johnriley

Link Posted 23/08/2010 - 13:51
Quote:
I see that many seem to have some problems in low light auto and manual focus. Use this; always focus with the longest range of your zoom lens then zoom out to the zoom setting that you want to use. Ie. 18 -85 lend focus at 85 zoom out to 18.....same for any lens. Works well.

That would work well if zooms were true zooms, but most these days are not. They are varifocal lenses, not parfocal zooms.

What this means is that they need refocusing at every focal length selected. You will only get away with this if it's a very small aperture and DOF covers the error created as you zoom.
Best regards, John

Dr. Mhuni

Link Posted 23/08/2010 - 14:25
Quote:
I've still had no satisfactory explanation as to how to make my 12-24 focus - even on infinity (which isn't that far away on that) in anything other than bright sunshine.

I've always found the 12-24 to be very good at AF (on a K2D). So perhaps your KX theory is right, Flossie. Though it sounds rather strange - surely JR's hunch that there's a fault with the lens is much more likely?
Mhuni

500px

flossie

Link Posted 23/08/2010 - 18:11
ChrisA wrote:

Feel free to stop by sometime soon and see if it's the same on my K10D.

Thanks ChrisA for the offer - but I need to spend some time first trying to find out if its just Operator Error - see if I can get a reproducable scenario that it won't focus properly in first, because it only seems to happen when I'm not expecting it!
Still shooting in the dark (literally and metaphorically)...
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